Trouble Overclocking 6970 past 900 Core

[BTC_Junkie]

This may have been discussed in the past but I've been searching the forum for 2 days and haven't found anything.

I'm currently running a Diamond 6970 http://www.newegg.com/Product/Product.aspx?Item=N82E16814103182&cm_re=6970-_-14-103-182-_-Product and having a trouble getting the card to Clock over 900. The card is running fine at 900/300 around 370 GHash/sec.  As soon as I move the clock over 900 (even to just 901) it drops to around 330 Ghash, and drops even further the higher it's clocked.  The card appears to be stable at higher clocks except for the GHash issue. Aticonfig reports that the overclocking is running correctly for the core, but memory is displaying at around 150.  I flashed the BIOS because I was unable to get the memory below 1275 with the factory BIOS, but even with the stock BIOS the same problem was happening over 900 core clock.

This is all running on Ubuntu 11.04, Catalyst 11.6, SDK 2.4, and phoenix (latest phatk kernel). I'm running several other 58XX cards in the same system and have not run into any problems.  Any idea what is happening here?

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[Trini8ed]

If a 6970 could get 330 ghash I wouldn't card to go any higher

[Jazkal]

http://forum.bitcoin.org/index.php?topic=9544.msg325307#msg325307

I have mine running at 429 Mh/s each.

Core: 970Mhz
Mem: 360Mhz
Fans: 100%
Powertune: +5%
Temps run anywhere from 64C to 69C

Running guiminer(newest) with Phoenix:
-k phatk VECTORS BFI_INT WORKSIZE=128 FASTLOOP=false AGGRESSION=12

I'm on Windows, so I don't know what tool you use to get the powertune settings set on linux, but without setting powertune to at least 5%, my numbers drop down to what you are seeing.

[truvativ]

i have 2 6950 with unlocked shaders (basically a 6970) in my windows server machine and with clocks at 960MHz/625MHz and voltage at 1200mV i get a stable 410MH/s per card. using MSI afterburner.
reference design. fans at 80%. both cards top off around 68-72*C
i would get like 380MH/s with mem down under 400. but when i tried 600 it went to 400MH/s. and 625 410MH/s. and 650 back down to 400MH/s
it's all about finding the mem sweet spot.

[BTC_Junkie]

Thanks for the help guys.  From your suggestions I started investigating voltages, but it didn't seem to be recognizing the increased V.

Then I stumbled on this thread:
http://forum.bitcoin.org/smf/index.php?topic=8384.0

Apparently the power control downclocks the card over 900 unless you modify the powercontrol options.  I set it to +20 and I'm getting 390 at 900 clock now.

Thanks!